The recovery of base metals from sulphide ores by bacterially assisted heap leaching is presently restricted to secondary copper sulphide minerals, such as chalcocite and covellite. Chalcopyrite, a primary copper sulphide mineral, is a notable exception and can not presently be successfully leached in a heap. The common practice with chalcopyrite ores is to produce a concentrate by froth flotation, for feeding to a smelter.
Attempts to leach chalcopyrite in weak to moderately strong sulphuric acid solution, with the addition of ferric as an oxidant, results in the surface passivation of the chalcopyrite, causing the reaction to either stop, or slow down to an unacceptable rate. Similarly, attempts to leach chalcopyrite with bacteria are hindered by the same surface passivation phenomenon. The mechanism by which this passivation occurs, and the nature of the passivating layer itself, is not fully understood.
The method of the present invention has as one object thereof to overcome the abovementioned problems associated with the prior art, or to at least provide a useful alternative thereto.
The preceding discussion of the background art is intended to facilitate an understanding of the present invention only. It should be appreciated that the discussion is not an acknowledgement or admission that any of the material referred to was part of the common general knowledge in Australia as at the priority date of the application.
Throughout this specification, unless the context requires otherwise, the word “comprise”, or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.